Mobile phase and Chromatographic systemPrepare as directed in the Assay under Dipyridamole Tablets.

Test preparation APrepare a solution of Dipyridamole in methanol having a known concentration of 1 mg per mL.

Test preparation BDilute 1.0 mL of Test preparation A with methanol to 100 mL, and mix.

ProcedureInject 10 µL of Test preparation B into the chromatograph by means of a sampling valve, adjusting the operating parameters so that the response of the main peak (retention time about 6.5 minutes) obtained is about 5% full scale. Inject 10 µL of Test preparation A, and run the chromatograph for 10 minutes: the sum of responses of all secondary peaks obtained from Test preparation A is not greater than the response of the main peak obtained from Test preparation B (1.0%).

AssayTransfer about 450 mg of Dipyridamole, accurately weighed, to a 250-mL beaker, and dissolve in 50 mL of glacial acetic acid. Stir for 30 minutes. Add 75 mL of acetone, and stir for an additional 15 minutes. Titrate with 0.1 N perchloric acid VS, determining the endpoint potentiometrically, using a glass electrode and a silver-silver chloride reference electrode system. Perform a blank titration, and make any necessary correction. Each mL of 0.1 N perchloric acid is equivalent to 50.46 mg of C24H40N8O4.